Unlock iPhone 4/3GS on iOS 4.3.3 Using Ultrasn0w 1.2.3 [How-To Guide]

iPhone Dev-Team has just released Ultrasn0w 1.2.3 to unlock iPhone 4 and iPhone 3GS on iOS 4.3.3. For those who don't know, Apple introduced a newASLR security feature in iOS 4.3.x which broke Ultrasn0w 1.2 naively using 0x1000 as the main executable base address. Now that iPhone Dev-Team has fixed Ultrasn0w 1.2 on iOS 4.3.3 by releasing Ultrasn0w 1.2.3, you can use it to unlock your iPhone on iOS 4.3.3 with old baseband.

Supported Basebands: 04.26.08 05.11.07 05.12.01 05.13.04 01.59.00 06.15.00 05.14.02 via 06.15.00 » 05.15.04 via 06.15.00 » 05.16.01 via 06.15.00 » 05.16.02 via 06.15.00 »

Unsupported Basebands: 05.14.02 05.15.04 05.16.01 05.16.02 02.10.04 03.10.01 04.10.01

Steps to Unlock iPhone 4/3GS on iOS 4.3.3 with Ultrasn0w 1.2.3:

1. Open Cydia app on your jailbroken iPhone. Wait while it reloads and updates its cache.

2. Tap on the Manage tab at the bottom of Cydia and then tap on Sourcessection to view your current Cydia repos. If you seerepo666.ultrasn0w.com already added in your current sources list, jump to step 4 otherwise continue to the next step.

3. Tap on the Edit button on the top-right corner followed by a tap on Addbutton on the top-left corner. When Cydia will prompt you for the repo address, enter http://repo666.ultrasn0w.com as Cydia/APT URL and hit Add Source button.

4. Now wait while Cydia updates its sources database. Once done, tap on the Search tab at the bottom of Cydia and type Ultrasn0w in the search field. As other 3rd-party Cydia repos also host Ultrasn0w, so make sure you download it from official Ultrasn0w repo as shown in the screenshot below:

5. Select Ultrasn0w from the search results and tap on Install button on the top-right. The DEB file of Ultrasn0w 1.2.3 is around 14.3 KB in size.

6. Now wait while Cydia installs Ultrasn0w on your iPhone. Once Ultrasn0w installation gets complete, tap on the Reboot Device button to restart your iPhone.

NOTE: Those iPhone users who do not rely on an unlock but still upgraded to iOS 4.3.3 while preserving their old basebands will get 1-signal-bar on iOS 4.3.3. To fix this signal-bars issue, you MUST install Ultrasn0w 1.2.3 on your iPhone.

UPDATE#1: For some reason, iPhone 3GS users with iPad basebands are still not able to unlock their iPhone on iOS 4.3.3 using Ultrasn0w 1.2.3  If anyone have got any fix, please share in the comments section below.